1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to canceling interference from a received signal.
2. Introduction
A wireless multiple-in-multiple-out (MIMO) system simultaneously supports communication for multiple users (e.g., access terminals). An access point (e.g., a base station) of a MIMO system employs multiple antennas for data transmission and reception while each user employs one or more antennas. The access point communicates with the users via forward link channels and reverse link channels. A forward link (or downlink) channel refers to a communication channel from a transmit antenna of the access point to a receive antenna of a user, and a reverse link (or uplink) channel refers to a communication channel from a transmit antenna of a user to a receive antenna of the access point.
MIMO channels corresponding to transmissions from a set of transmit antennas to a receive antenna are referred to spatial streams since precoding (e.g., beamforming) is employed to direct the transmissions toward the receive antenna. Consequently, in some aspects each spatial stream corresponds to at least one dimension. A MIMO system provides improved performance (e.g., higher throughput and/or greater reliability) through the use of the additional dimensionalities provided by these spatial streams.
Under certain circumstances, a spatial stream directed to a given receive antenna causes interferences at another receive antenna due to, for example, the beamforming being less than ideal. One method of reducing this interference involves using multiple receive antennas at each user and employing interference-cancellation such as minimum mean square error (MMSE) spatial filtering. However, such an approach is undesirable in some cases (e.g., due to the need for multiple receive antennas). Consequently, there is a need for improved techniques for mitigating interference caused by spatial streams.